In the United States, about 10% of the population will suffer from back pain sometime in the next year. This occurrence is more than any other injury or disease except for the common cold and flu. About one-third of those suffering from back pain will not recover and will live with persistent, disabling symptoms. These numbers are cumulative year after year.
One root cause of back pain, particularly the persistent and disabling kind, is problems (including arthritis) with facet joints. The back of each vertebra has two sets of facet joints. One pair faces upward and the other pair faces downward. Within each set there is a facet joint on the left side of each vertebra and a facet joint on the right side of each vertebra.
Facet joints are the system of joints that allow movement (forward bending, backward bending and twisting) of the spine. While these joints allow movement of the spine, their interlocking nature also helps to stabilize the spine.
Similar to other joints in the body, each facet joint is surrounded by a capsule of connective tissue and produces synovial fluid to nourish and lubricate the joint. The joint surfaces themselves are coated with a thick spongy material called articular cartilage that enables the bones of each joint to smoothly move against the other.
Osteoarthritis is probably the most common cause of facet joint pain. This degenerative disease causes progressive cartilage deterioration. Without the spongy cartilaginous cushion, joint bones begin to rub against each other when at rest and during movement causing a substantial amount of pain. Therefore, one option to treat this type of pain is to join rubbing portions of bone together so that this painful friction does not occur.
Present surgical solutions available for facet joint dysfunctions are high-risk, complex and invasive pedicle screw or compression screw based operations associated with prolonged recovery times (such as from about 6 to 24 months; see, e.g., U.S. Pat. No. 6,485,518 and U.S. Pat. No. 6,648,893). The high risk nature of these surgeries leads to uncertain clinical outcomes which can motivate doctors and patients to choose non-surgical symptomatic treatments. While these treatments can help to alleviate back pain temporarily, the underlying cause of the pain continues to progressively worsen. Moreover, there are additional problems associated with screw-based approaches to facet joint fusion. For example, screw-type fixations can work their way loose over time, negating any beneficial effect of the original procedure. Thus, there is room for great improvement in the surgical treatment of facet joint dysfunction.